1. Field of the Invention
This invention relates to novel organosilicon compounds. More particularly, this invention relates to novel organosiloxane compounds that impart excellent adhesion to elastomers and gels prepared from organosiloxane compositions that cure by a platinum-catalyzed hydrosilation reaction. The adhesion promoters are particularly effective at relatively low curing temperatures, particularly from ambient up to 70.degree. C.
2. Background Information
A variety of silanes and organosiloxane compounds have been proposed for use as primers and adhesion promoters with organosiloxane compositions that cure by a platinum-catalyzed hydrosilation reaction. These primers and adhesion promoters typically contain two types of reactive groups, one of which is a hydrolyzable group and the second is capable of reacting with either the Substrate to be adhered to or the ingredients of the organosiloxane composition that participate in the curing reaction. For example, the adhesion additives described in U.S. Pat. Nos. 3,772,026 and 3,873,334 are silanes containing acyloxy groups, such as acetoxy, and either a silicon-bonded hydrogen atom or an alkenyl radical. While the acyloxy group exhibits the desired high reactivity in the presence of moisture, the product of this reaction is a corrosive acid.
U.S. Pat. No. 4,196,273 teaches using alkoxysilanes containing ethylenically unsaturated groups, however there is no indication in the examples of this patent that adhesion can be achieved at curing temperatures below 100.degree. C. Using partial hydrolyzates of these silanes as adhesion promoters is described in U.S. Pat. No. 4,329,273. Compositions containing these hydrolyzates did not cure at ambient laboratory temperatures, but did cure at 100.degree. C.
Mixtures of an epoxy-functional alkoxysilane with a liquid silanol-functional polyorganosiloxane containing at least one alkenyl radical are described in U.S. Pat. No. 4,087,585, however there is no indication that compositions containing these adhesion-promoting additives can be cured at temperatures below about 100.degree. C. Adhesion promoting organosilicon compounds containing ethylenically unsaturated, epoxide and alkoxy groups are described in U.S. Pat. No. 4,732,932.
The use as adhesion promoters of organosilicon compounds containing the --COSi(OR').sub.3 group is described in U.S. Pat. Nos. 4,658,851; 4,719,262; and 4,906,686. The adhesion promoters are prepared by the reaction of an alkoxysilane with an ethylenically unsaturated alcohol. U.S. Pat. No. 4,906,686 has the additional requirement that the silane contain an organofunctional group such as epoxy or (meth)acryloxy in addition to alkoxy groups.
The following patents describe organosilanes or organosiloxane compounds containing a silicon-bonded alkenyl radical or silicon-bonded hydrogen atom in addition to silicon-bonded hydrolyzable groups and the use of these compounds as adhesion promoting additives for organosiloxane compositions that cure by a hydrosilation reaction: U.S. Pat. No. 4,786,701; European Patent Application (EPA) No. 449,181; Japanese Laid Open Patent Application No. 4,311,766; U.S. Pat. No. 4,721,764; EPA No. 458,355; and EPA No. 469,890.
A shortcoming of the adhesion promoters described in the preceding paragraphs is the lack of any indication that cohesive bonding of the composition to substrates can be achieved at curing temperatures below about 100.degree. C.
U.S. Pat. No. 3,887,602 describes reaction products of alkoxysilanes containing a silicon-bonded hydrogen atom and allyl ethers of polymerized aldehydes. These reaction products are useful as coupling agents for bonding glass fibers to polymers based on formaldehyde or trioxane. The reaction products can be represented by the formula (RO).sub.3 Si(CH.sub.2).sub.3 (OCH.sub.2 OR').sub.n OCH.sub.2 O(CH.sub.2).sub.3 Si(OR).sub.3, where R represents methyl or ethyl, R' is ethylene or n-butylene and the value of n is between 8 and 56.
One objective of this invention is to provide a novel class of organosiloxanes that will cohesively bond organosiloxane compositions to a variety of substrates during curing of the compositions by a platinum group metal catalyzed hydrosilation reaction at temperatures as low as 25.degree. C.